Double-sided lens sheet and projection screen

ABSTRACT

In order to provide a dual-surface lens sheet in which a color shift is reduced and positions of unit lenses on a front surface and a back surface are easily aligned even if the unit lenses are disposed in fine pitch when used for a rear projection screen which is used for a display device using a plurality of projector as light sources, a half-column-cylindrical-convex-lens is used in a lens sheet having lens sections on front surface and a back surface such that pitch ratio for disposing the unit lenses on the front surface and the back surface is in a range of 1:2 to 1:30 and disposition directions of the lens sections are uniform.

TECHNICAL FIELD

[0001] The present invention relates to a lens sheet which is effectivewhen it is used for an image displaying screen (hereinafter called atransmission projection screen, or a rear projection screen) to be usedfor a rear projection television.

BACKGROUND ART

[0002] Commonly, in a transmission projection screen, a Fresnel lenssheet and a lenticular sheet are assembled.

[0003]FIG. 15 is a general view for a television having conventionalthree-tube projector. In FIG. 15, reference numerals 51, 52, and 53indicate image projection devices for colors such as R, G, and B.Reference numeral 54 indicates a mirror. Reference numeral 55 indicatesa transmission projection screen.

[0004] A Fresnel lens sheet in FIG. 16 emits a light (which dispersesfrom a small-diameter lens) which is projected from a projector to alenticular sheet 57 as an approximate parallel light by using aconverging lens.

[0005] The lenticular sheet 57 widens horizontally a range of theprojected light which is incident as an approximate parallel light bythe Fresnel lens sheet 56 so as to emit to a person who observes thelight by using a characterized feature of a cylindrical lens group whichare disposed in horizontal direction.

[0006] Also, in a rear-projection screen, customarily, a light diffusinglayer is formed for purposes of widening a display light in a verticaldirection, making the projected light from the projector focused, andreducing unnecessary blinking which is called a scintillation in theimage because of small diameter of the lens in the projector.

[0007] The light diffusing layer is formed in at least any one among alenticular sheet, Fresnel lens sheet, or a front board such as aprotection board. For forming the light diffusing layer, methods such asapplying methods, layering methods, and mixing methods can be employedpreferably.

[0008] For a rear projection TV, according to a method which is used ina projector (light source), there are variations such as CRT methodaccording to the three-tube (R, G, B) method, liquid crystal method,reflection light bulb method which is otherwise called as adigital-micromirror-device (DMD, Trademark registered by TexasInstruments (TI) or digital-light-processing (DLP). Liquid crystalmethod and reflection light bulb method are in so-called a single-tubemethod in which there is one set of projector.

[0009] In a conventional lenticular sheet which is used in a rearprojection screen which is used for a rear projection TV according toCRT method, a lens section on a front surface and on a back surface arehalf-column-convex-shaped-cylindrical-lens-group in a uniformdisposition direction, the disposition pitch of the unit lenses on afront surface and a back surface is 1:1 under accurate alignmentcondition (not shown in the drawings).

[0010] The above structure is employed because the projected light fromeach projector is emitted under offset angle condition each other whenthree projectors for three colors such as R, G, and B are disposed in ahorizontal direction.

[0011] When the projected lights for R, G, and B are emitted from theprojectors under offset angle condition, images according to threeprimary colors are mixed without position shift. Thus, observable angleis limited. When viewpoint is moved horizontally, image looks somewhatin red or in blue. Such observation accompanied with changed color iscalled “color shift”.

[0012] In order to solve the color shift, it is necessary to adapt adual-surface lenticular sheet in whichhalf-column-cylindrical-lens-group are formed on a front surface and aback surface, the disposition pitch of the unit lens on the frontsurface and the back surface is in relationship of 1:1, unit lenseswhich are to be a pair on the front surface and the back surface areaccurately aligned.

[0013] Also, the shape of the unit lenses on the front surface and theback surface is designed by taking the refractive index corresponding tothe wavelength such that the scope of the image for primary colors suchas R, G, and B of which optical paths are slightly offset overlapping ina uniform optical intensity should be as large as possible.

[0014] In order to provide a high resolution image quality, in the lenssheet contained in the screen, narrow pitch (fine pitch) disposition inthe unit lens is required. In order to produce adual-surface-lenticular-sheet, alignment in the unit lens on the frontsurface and the back surface is more difficult.

[0015] Also, along with realization in finer resolution in paralleldisposition pitch for a unit lens, finer resolution for a lighttransmitting section in a shading pattern (Black Matrix hereinaftercalled BM) which is formed away from the lens section has been realized.Therefore, accuracy for forming an aperture section in a lightcondensing section where a light is condensed by the micro-lens arraysection clearly is required.

[0016] In case of a lens sheet having a fine pitch lens section, a blackmatrix is formed by so called a self-alignment method in which positionsof non-light-condensing section for the lens are determined accuratelyby using light condensing characteristics by the lens to aphotosensitive resin layer which is formed on the lens sheet away fromthe lens.

[0017] For self alignment method, there are a wet method in which theshading pattern is formed after developing the exposed photosensitiveresin layer, or a dry method in which the shading pattern is formedapplying a color without developing the exposed photosensitive resinlayer.

[0018] In dry method, a photosensitive adhesion agent having acharacteristics in which bonding characteristics occurs according towhether or not light is exposed is used, and a color is appliedcorresponding to the adhesion.

[0019] In order to form a BM having preferable shading ratio (forobtaining preferable contrast in image, a range such as more than 60% isexperimentally preferable) for a transmission liquid crystal projectionscreen, the position of light condensation (focus) by the lens sectionis set preferably according to the shading ratio in the formed patternin the photosensitive resin layer not on the light emission of thephotosensitive resin layer.

[0020] In a case in which a lens is spherical, positions of focal pointare different between in the center of the lens and marginal area of thelens according to aberration. Therefore, in a case in which the shadingpattern is formed by the self alignment method, the position where thecharacteristics of the photosensitive resin layer changes cannot bedetermined precisely. Therefore, a borderline between the aperturesection and the shading section is hardly clear.

[0021] In particular, in a case in which the shading ratio is enhancedso as to realize an image with higher contrast, there is a problem inthat it is difficult to form a BM having a clear borderline between afine aperture section and the shading section when parallel dispositionpitch between the unit lens is very fine and each one of the unit lensis fine.

[0022] In a conventional light transmission screen which is used in arear-projection television which is sold in a market, it is common thata Fresnel lens having a concentric gaps are formed on one surface and alenticular lens in which cylindrical lenses are disposed in onedirection are provided. A case in which either one of them is used isacceptable. Also a case in which a light diffusing layer is provided onother member can be common.

[0023] In members which is contained in these transmission screens,optical disposition is arranged such that the lights which are emittedfrom the projector are in approximate parallel state by the Fresnel lensso as to obtain horizontal perspective angle by widening the emittedlight in a horizontal direction in the image by the lenticular lens andvertical perspective angle by widening the emitted light in a verticaldirection in the image by the light diffusing member.

[0024] Furthermore, a transmission screen which can obtain a brighterand clearer image quality is known by replacing the lenticular lens by amicro-lens sheet which can obtain the horizontal perspective angle andthe vertical perspective angle compatibly without using the lightdiffusing member and by discontinuing or reducing the use of the lightdiffusing member.

[0025] Also, a method in which two lenticular layers are used such thatlongitudinal directions of the cylindrical lenses are orthogonal, or amethod in which the cylindrical lenses are disposed on both surfaces ofone base member layer such that the longitudinal directions of thecylindrical lenses are orthogonal are known.

[0026] Also, a structure in which a shading layer having aperturesections is provided in a light condensing section of each of thecylindrical lens contained in the lenticular lens or in the lightcondensing section of each of the micro-lens contained in the micro-lensarray sheet so as to improve S/N ratio of the screen is known.

[0027] Also, there is a case in which a hardcoat layer or aanti-reflection layer (hereinafter called AR layer) are provided anoutermost surface according to a usage of these transmission screen.

[0028] In a transmission screen using a conventional lenticular sheet ora micro-lens sheet, a lenticular layer and a diffusion layer arecombined so as to control the perspective angle in a horizontaldirection and a vertical direction. In the micro-lens array, widerperspective angle is necessary; therefore, there are disadvantages suchas deteriorated quality in the image due to absorption of light by thediffusion layer and white scattering, and reduced screen gain caused bywide diffusion.

[0029] Also, it is possible to propose to control the perspective anglein a horizontal direction and a vertical direction by using twolenticular layer in which longitudinal direction of each cylindricallenses are orthogonal, or by disposing a plurality of cylindrical lenson both surfaces of one base member layer such that longitudinaldirections of each of the cylindrical lens are orthogonal. In suchcases, quantity of the members contained in the cylindrical lens becomesdoubled, and very fine manufacturing process for lens also becomesdoubled. Thus, there is a problem in that cost for parts andmanufacturing process become expensive.

[0030] Also, in a screen in which two lenticular lenses are disposed onone plane surface so as to be orthogonal each other, two lenticularlenses overlap each other. Therefore, if shape of one lenticular lenschanges, optical characteristics in the other lenticular lens changesaccordingly. Thus, it is not possible to control the perspective angleby independently changing the shape of one of the lenticular lenses.Therefore, there is a limit for controlling range for the perspectiveangle; thus, such a limit is not preferable from practical point ofview.

[0031] Furthermore, in order to use a micro-lens array for atransmission screen, it is necessary to produce in a worthwhile size forthe purpose such as 50 inches in diagonal plane. In such a case, a lensthug (thickness of refractive surface) having nearly half a diameter ofan element lens is necessary for obtaining wider perspective angle.However, it is difficult to compatibly realize such depth in lens thugand picture size because of the depth to be molded. Because of this,even if necessary optical performance can be realized as long as animage area is small, due to a problem in manufacturing process, it isdifficult to enlarge the image area.

DISCLOSURE OF INVENTION

[0032] A main object of the present invention is to provide adual-surface lens sheet such that the color shift is reduced when it isused for a rear projection screen which is used in a displaying devicein which a plurality of projector such as three-tube CRT projector areused as light source, it is easy to align the position of the unitlenses on the front surface and the back surface even if the unit lensesare disposed in fine pitch; thus the difficulty in the manufacturingprocess does not increase.

[0033] Yet, another object of the present invention is, in a micro-lenssheet which is preferable for a lens sheet to be used for a transmissionprojection screen having two lens sheets in combination particularlywith a Fresnel lens, to provide a micro-lens sheet in which the unitlens group is disposed in a pitch as fine as 200 μm or finer, and it ispossible to control such that the perspective scope of the emissiondirection of the display light by the lens section can be wide.

[0034] Yet another object of the present invention is to provide amicro-lens sheet which can easily form a fine BM in which a borderlinebetween an aperture section and the shading section is clear when a BMhaving a high shading ratio (75%) is formed on a micro-lens sheet awayfrom the lens section.

[0035] Yet another object of the present invention is to provide aprojection screen using a micro-lens having sufficient opticalcharacteristics for a screen with less optical absorption, less gainreduction, and controlled white scattering easily with large area.

[0036] Yet another object of the present invention is to provide aprojection screen using a micro-lens of which material cost andmanufacturing cost are inexpensive.

[0037] A first aspect of the present invention is a dual-surface lenssheet having periodical gaps contained in a lens sections on a frontsurface and a back surface in a lens sheet wherein pitch ratio of theunit lens on the front surface and the back surface is in a range of 1:1to 1:30.

[0038] The lens sections on the front surface and the back surface inthe dual lens sheet are usually used in aspects such as; (1) in ahalf-column-cylindrical-convex-lens of which disposition directions areuniform; (2) in a micro-lens array section in which the unit lenses arein secondary dimensional approximate matrix disposition; and (3) in amicro-lens array section in which one of the unit lens is ahalf-column-cylindrical-convex-lens and the other unit lens is made suchthat the unit lenses are in secondary dimensional approximatedisposition.

[0039] In a case of above (3), the pitch ratio in which the unit lensesare disposed in the a half-column-cylindrical-convex-lens and themicro-lens array section should preferably be in a range of 2:1 to 30:1.

[0040] It is acceptable that the micro-lens array section may be made ofa reacted hardened product of the radioactive-ray-curable-resin andinclude the unit lens having aspherical shape. Also, it is acceptablethat the micro-lens array section may have only a unit lens havingspherical shape. In order to dispose the unit lens groups in fine pitch,it is preferable to form the micro-lens array section by performing amolding operation by using the radioactive-ray-curable-resin.

[0041] It is also acceptable that the micro-lens array section may bemade only of the unit lens having spherical shape.

[0042] Any variation in disposition of the unit lens may be acceptable.A matrix disposition which is neatly disposed in grid form, a deltadisposition in which the distance between the unit lenses is uniform, ahoneycomb disposition in which shape of the unit lens is a hexagon usingthe delta disposition can be acceptable. Also, a disposition in which anarray n and an array n+1 (n is an integer) contained in the lens arraysection in the matrix disposition are in an offset disposition by half apitch. A shape of the unit lens area may be a rectangle or a triangle. Atriangle formed by neighboring unit lens areas can be a regular trianglesometime, and it cannot be a regular triangle sometime. By using suchdifferent cases, it is possible to change the light diffusioncharacteristics in a horizontal direction and a vertical direction.

[0043] It is acceptable that, in the micro-lens array section, opticaldiffusion by the lens function in each unit lens is different in ahorizontal direction and a vertical direction.

[0044] In order to produce the above dual-surface lens sheet easily, itis necessary that periodical gaps are formed for forming the lenssection on one surface of the micro-lens sheet, the other surface isflat, the lens sheets are layered such that the flat surfaces of eachsheet are corresponding.

[0045] It is preferable that, in a micro-lens sheet, a shading layer isformed in an area corresponding to a non-light-condensing section byeach unit lens on a flat surface of at least one of the lens sheet awayfrom the lens section so as to improve the contrast in the displayimage.

[0046] It is acceptable that, in a dual lens sheet, a unit lens havingconvex shape is disposed in the lens section, a focusing surface of atleast one of the lens section exists in the dual lens sheet, parallellights which is incident to one of the unit lens pass through aplurality of unit lens in the other lens section when emitted from thelens section in the other lens section.

[0047] A rear projection screen in which a dual-surface lens sheetaccording to any one of the above aspects and a Fresnel lens areassembled is characterized in that, a lens section in which the unitlens in the dual lens sheet is disposed in larger pitch and the lenssection in the Fresnel lens sheet are faced such that the Fresnel lenssheet is disposed near a plurality of projector (light source).

[0048] The above rear projection screen is preferable to be used in adisplay device having a light source of the three-tube CRT projector.The theory is explained as follows.

[0049] Optical characteristics of a “single face lens sheet” having alens section in which a unit lenses (convex lenses) are disposed on onlyone surface is shown in FIG. 1A. The image light is emitted from theprojector for B (blue) such that the display light is emittedperpendicularly toward a center of the single-face lens sheet from thelens section. Also, the image lights are emitted from the projectors forG (green) and R (red) under slightly offset condition disposed inhorizontal ends. Distribution in the brightness of each image lightwhich is emitted from the flat surface on the other surface is shown inFIG. 1A.

[0050] In the drawing, a curve B indicates a symmetrical distributionhaving a peak in 0 degree. Curves G, and R indicate distributions inwhich peak is slightly offset from 0 degree. The region in which threeprimary colors are mixed uniformly is in a small range around 0 degree(in a horizontal direction in the drawing). Unless it is out of therange, green is strong in a left-hand side of the range, and red isstrong in a right-hand side of the range.

[0051] In FIG. 1B, optical characteristics in the “dual-surface lenssheet” according to the present invention having a lens section in whichthe unit lenses (convex lenses) are disposed on both surfaces is shown.

[0052] In the dual-surface lens sheet, comparing to a case in which theemission surface is flat, a range in which the parallel lights which areincident from one of unit lens disposed in incident area refracts to beemitted is broadened. The curve which indicates the brightnessdistribution for each color is softly wide in horizontal directions. Thecenter of the range in which the three-primary colors are uniformlymixed is in 0 degree. Such a range is wider than the case shown in FIG.1A (in horizontal direction in the drawing). The image stronger in greenand the image stronger in red can be observed in wider angle than in thecase of FIG. 1A.

[0053] This means that the color shift can be reduced. In order toreduce the color shift further, it is necessary to broaden the range inwhich the three-primary-colors are uniformly mixed so as to reduce areashaving strong green and strong red.

[0054] In order to broaden the range in which the parallel lights whichare incident from one unit lens in the incident side refract to beemitted, by simply using a single-face lens sheet in which thedisposition angle by the unit lens in the incident side is broadened,similar effect can be obtained. However, it is difficult to produce alens sheet having a lens which focal length is short. Therefore, it isdifficult to control the mixture ratio for the three-primary-colors.Thus, in order to realize the above effect, it is preferable to use thedual-surface lens sheet.

[0055] In every aspect of the present invention, in order to dispose theunit lens groups in highly fine pitch, it is preferable to form themicro-lens array section by using the radioactive-ray-curable-resin.

[0056] In this aspect of the present invention, it is acceptable that amicro-lens sheet has a micro-lens array section in which unit lenses aredisposed in approximate matrix in a second dimensional manner on atleast one surface of a base board wherein the micro-lens array sectionis formed such that a reacted product of a radioactive-ray-curable-resinis bonded on only one surface of the base board, the micro-lens arraysection includes the unit lens having an aspherical shape, anddisposition pitch of neighboring unit lenses is 100 μm or shorter.

[0057] It is acceptable that, in a micro-lens sheet, the micro-lensarray section has only the unit lens having aspherical shape.

[0058] Any variation in disposition of the unit lens may be acceptable.A matrix disposition which is neatly disposed in grid form, a deltadisposition in which the distance between the unit lenses is uniform, ahoneycomb disposition in which shape of the unit lens is a hexagon usingthe delta disposition can be acceptable. Also, a disposition in which anarray n and an array n+1 (n is an integer) contained in the lens arraysection in the matrix disposition are in an offset disposition by half apitch. A shape of the unit lens area may be a rectangle or a triangle. Atriangle formed by neighboring unit lens areas can be a regular trianglesometime, and it cannot be a regular triangle sometime. By using suchdifferent cases, it is possible to change the light diffusioncharacteristics in a horizontal direction and a vertical direction. Inorder to improve contrast in a displayed image which is supposed to beobserved in a rear projection screen, it is preferable that a shadinglayer is formed on a position on a surface of the base board which isdisposed away from the micro-lens array section where a light is notcondensed by each of unit lens.

[0059] A second aspect of the present invention is a micro-lens sheethaving a micro-lens array section in which unit lenses are disposed inapproximate matrix in a second dimensional manner on at least onesurface of a base board wherein diameter for each of the unit lens andthe disposition pitch is 200 μm or shorter, light emission angle whichis emitted from each unit lens is more than ±30 degrees against a normalof a main surface of the micro-lens sheet; chromatic difference ofmagnification which is caused by each unit lens is designed to be in arange of 0% <chromatic difference of magnification ≦50% of the diameterof the lens.

[0060] A third aspect of the present invention is a projection screenhaving the micro-lens sheet having the micro-lens array section in whichthe unit lenses are disposed in an approximate matrix in asecond-dimensional manner wherein a surface of the unit lens is formedin toric shape as a continuous surface such that curvature of crosssectional shape of the unit lens in one direction is smaller than thatin an orthogonal direction to the particular direction, the micro-lensarray section in which the unit lens is disposed in an approximatematrix in a second-dimension manner is formed on one surface of thetransparent sheet, and the shading layer having the aperture section ofwhich optical axis is aligned with the optical axis of unit lens groupon a surface of the sheet which is disposed opposite to the micro-lensarray section.

[0061] In a fourth aspect of the present invention, it is characterizedin that, in a projection screen, directions of the curvature of eachunit lens are uniformly disposed when the micro-lens array section inwhich the unit lens is disposed in an approximate matrix in asecond-dimension manner is formed on one surface of the transparentsheet.

[0062] In a fifth aspect of the present invention, it is characterizedin that, in a projection screen, lens thug of the toric surface which isa ratio between thickness of a curvature section in a one direction andthickness of a curvature section in a cross sectional surface in anorthogonal direction is ⅔ or smaller.

[0063] In a sixth aspect of the present invention, it is characterizedin that, in a projection screen, lens thug of the toric surface which isa ratio between thickness of a curvature section in a horizontaldirection and thickness of a curvature section in a cross sectionalsurface in a vertical direction is ⅔ or smaller.

[0064] In a seventh aspect of the present invention, it is characterizedin that, in a projection screen, the micro-lens array section is formedon one surface of the transparent sheet which is disposed in an areafrom which a light is incident (near a projector) when the micro-lensarray section is used for a transparent projection screen.

[0065] In an eighth aspect of the present invention, it is characterizedin that, in a projection screen, the shading layer is formed in thenon-light-condensing area on a surface of a base board opposite to thelens such that a light does not condense by exposing a light through themicro-lens array section, the photosensitive resin layer or a layerwhich is formed on a surface of the photosensitive resin layer is a baseboard for a lens such that the refractive index of the layer is lowerthan that of the transparent sheet.

[0066] In a ninth aspect of the present invention, it is characterizedin that, in a projection screen farther has a Fresnel lens having aconcentric ring band near a light incident region (near a projector)when the projection screen according to a first aspect of the presentinvention is used for a transparent projection screen.

BRIEF DESCRIPTION OF DRAWINGS

[0067]FIG. 1A is a graph showing an optical characteristics of the“single-face lens sheet” having a lens section in which the unit lens(convex lens) is disposed only on one surface. FIG. 1B is a graphshowing an optical characteristics of the “double-face lens sheet”according to the present invention having lens sections in which theunit lenses (convex lenses) are disposed on both surfaces.

[0068]FIGS. 2A to 2D are views showing shapes of the unit lens sectionof the double-face lens sheet according to the present invention.

[0069]FIG. 3A is a cross section showing an optical path in a case inwhich a unit lens has a spherical shape (conventional technique). FIG.3B is a graph showing chromatic difference of magnification.

[0070]FIG. 4A is a cross section showing an optical path in a case inwhich a unit lens has an aspherical shape as defined as the presentinvention. FIG. 4B is a graph showing chromatic difference ofmagnification.

[0071]FIGS. 5A and 5B are cross sections showing an example for thedouble-face lens sheet according to the present invention.

[0072]FIG. 6 is a curve showing an example for a cross sectional shapeof a unit lens according to the present invention in which there is lesschromatic difference of magnification.

[0073]FIG. 7 is a graph showing a distribution of exposure on a BMsurface in case in which a unit lens has an aspherical shape as definedin the present invention.

[0074]FIGS. 8A and 8B are general views for a micro-lens sheet used in aprojection screen according to the present invention.

[0075]FIG. 9 is a perspective view of an element lens contained in themicro-lens array sheet used in the projection screen according to thepresent invention.

[0076]FIG. 10 is a cross section of an element lens in a horizontaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0077]FIG. 11 is a cross section of an element lens in a verticaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0078]FIG. 12 is an example for a rear projection display device usingthe dual-surface lens sheet according to the present invention.

[0079]FIG. 13 is a view showing a structure for a screen in theprojection display device using the dual-surface lens sheet according tothe present invention.

[0080]FIGS. 14A to 14C are general views showing each embodiment of thedual-surface lens sheet according to the present invention.

[0081]FIG. 15 is a general view for a television which is provided witha conventional three-tube projector.

[0082]FIG. 16 is a view showing a structure of screen shown in FIG. 15.

BEST MODE FOR CARRYING OUT THE INVENTION

[0083] In the present invention, it is necessary that the pitch in whichthe unit lens of the lens section 32 near the observer (in right-handside in the drawing) should be ½ or lower than the pitch in which theunit lens of the lens section 31 near the projector and the Fresnel lens(left-hand side in the drawing).

[0084] If the above condition is satisfied, at least one unit lens nearthe observer corresponds to one unit lens near the projector and theFresnel lens. Therefore, even if strict aligning operation is notperformed, the light which is incident to one of unit lens near the lenssection 31 orthogonally is emitted through the unit lens in the lenssection 32 (FIGS. 5A, 5B).

[0085] In FIG. 5A, the position of the focal length of the parallellight which is incident to one of the unit lens near the lens section 31orthogonally is near a top of the one of the unit lens near the lenssection 32, that is, an approximate emission surface on the dual-surfacelens sheet.

[0086] In the drawing, the unit lenses on an incident surface and anemission surface are in a relationship of 1:1. Thus, the parallel lightwhich is incident to one of the unit lens near the lens section 31 underoffset manner from the perpendicular angle is emitted through other unitlens which neighbors the lens section 32. Therefore, the unit lenses onan incident surface and an emission surface are in a relationship of1:1.

[0087] The light which is incident under offset manner is equivalent toan image light from the projector of which incidence angles aredifferent.

[0088] In FIG. 5B, the position of the focal length of the parallellight which is incident to one of the unit lens near the lens section 31orthogonally exists in the dual-surface lens sheet. When the parallellight which is incident to one of the unit lens is emitted, the parallellight passes through a plurality of the unit lens near the lens section32.

[0089] In the drawing, a dual-surface lens sheet in which a lens sheeton one of which surface a lens section 31 is formed and the othersurface is flat and a lens sheet on one of which surface a lens section32 is formed and the other surface is flat are layered such that bothflat surfaces correspond is shown. The position of the focus isequivalent to an approximate flat surface of the lens sheet on which thelens section 31 if formed.

[0090] In the drawing, the unit lenses on an incident surface and anemission surface are in a relationship of 1:n (n is an integer largerthan 1).

[0091] Before explaining embodiments of the invention, here,light-condensing characteristics corresponding to a shape of the unitlens and chromatic difference of magnification are explained.

[0092]FIG. 3A is a cross section showing an optical path in a case inwhich a unit lens has a spherical shape (FIG. 3A) and a graph showingchromatic difference of magnification (FIG. 3B). FIG. 4A is a crosssection showing an optical path in a case in which a unit lens has anaspherical shape as defined as the present invention. FIG. 4B is a graphshowing chromatic difference of magnification.

[0093] According to FIG. 3, parallel lights which are incident to a unitlens 10 from a left-hand-side of the drawing are incident to a surfaceof a unit lens, and the parallel lights are refracted, then the parallellights are condensed so as to be focused in a right-hand-side of thedrawing. After that, the light is emitted so as to be spread in verticaldirection as shown in the drawing.

[0094] In this case, the focal length of the lights which are incidentin a central area of the unit lens is long (position of focus point isin a right-hand-side in the drawing), and the focal length of the lightswhich are incident in a marginal area of the unit lens is short(position of focus point is in a left-hand-side in the drawing) becauseof aberration due to a spherical lens. This is called an axial chromaticaberration.

[0095] On the other hand, because of aberration due to a spherical lens,a graph for showing a chromatic difference of magnification: FIG. 3A isobtained under condition that a center of the unit lens is plotted in ahorizontal axis such that y=o, and a distance between a position where athe emitted light and a light emitting surface cross is plotted as Δ yon a vertical axis (EY) such that when y=0, then Δ y=0.

[0096]FIGS. 4A and 4B show a case in which the unit lens has a shape inwhich there is less aberration due to spherical lens. As shown in FIG.4A, in this case, focus points approximately coincide over a central areto marginal area on the unit lens (there is a less axial chromaticaberration). Accordingly, FIG. 4B indicates that there is a littlefluctuation in EY; thus, there is less chromatic difference ofmagnification.

[0097]FIG. 6 is a curve showing an example for a cross sectional shapeof a unit lens according to the present invention in which there is lesschromatic difference of magnification.

[0098] Here, in the micro-lens sheet according to the present invention,its usage is not limited to a transmission projection screen. That is,the micro-lens sheet according to the present invention can be used fora light guiding member for controlling a lighting light from the lightsource in a uniform brightness and in a uniform emission direction in adisplay screen in a display having a built-in light source such as abacklight in a non-large size (30 inch size like in atransmission/reflection projection screen) transmission projectionscreen.

[0099] Operation

[0100] According to optical characteristics corresponding to shape of anunit lens, in case of rear projection screen, it is preferable thatemission direction of the display light is controlled so as to be wideto an optical axis (normal direction to a screen main surface) in thatthe perspective scope can be widened without depending on lightdiffusing agent and a cost for a screen does not increase because a lotof light diffusing agent is not necessary.

[0101] In the present invention, light emission angle of each lens iswider than ±30 degrees to an optical axis; therefore, it is possible toobtain necessary perspective angle characteristics for a transmissionscreen. Furthermore, following operational effect is anticipated.

[0102] Improvement in BM Ratio

[0103] As explained above, BM pattern can be formed by using lightcondensing patter by self-alignment method in case in which parallellights are incident to fine lenses on a micro-lens sheet. In a fine unitlens having chromatic difference of magnification according to thepresent invention, it is possible to make an aperture area quite small.

[0104]FIG. 7 is a graph showing a distribution of exposure on a BMsurface in case in which a unit lens has an aspherical shape as definedin the present invention. Here, the shape of the light condensingsection is in a pulse wave form; thus, a borderline between the lightcondensing section and the non-light-condensing section is clear. Inorder to form BM by a self-alignment method, it is possible to recognizea shading layer forming section and a shading layer non-forming sectionaccording to whether or not there is an adhesive section of thephotosensitive adhesive easily. Therefore, it is possible to form ashading pattern clearly. By doing this, it is possible to obtain BMhaving high shading ratio (75% or higher); thus, it is possible toobtain a screen which can display high contrast image easily.

[0105] Under condition that a borderline between a surface on which BMis formed (in case of self-alignment method, a surface of photosensitivemember) and a base member for lens sheet is defined as a “focusingsurface”, by limiting the fluctuation range of the chromatic differenceof magnification in 50% of the diameter of a unit lens or lower, it ispreferable to form BM in 75% of BM area ratio (shading ratio) or higher.Furthermore, by limiting the fluctuation range of the chromaticdifference of magnification in 31% of the diameter of unit lens orlower, it is preferable to form BM in 90% of BM area ratio (shadingratio) or higher. Thus, it is possible to improve not only contrast butalso S/N greatly.

[0106] Improvement in Product Yield

[0107] When BM is formed by self-alignment method, more lights arecondensing because of smaller aberration due to spherical lens.Therefore, illumination in the exposed section increases; therefore, S/Nto an external light (non-parallel light emitted through the unit lens)improves. As a result, it is possible to obtain a lens sheet havingaccurate shading pattern which is quite independent to disturbance suchas the external lights.

[0108] Also, by disposing a lower refractive index layer than that ofthe lens sheet as a photosensitive member layer, and by adjusting thethickness of the lower refractive index layer, it is possible to adjustthe accuracy of BM easily.

[0109] Embodiments in the present invention are explained as followswith reference to drawings.

[0110] First Embodiment FIG. 12 is a cross section showing a generalstructure of a liquid crystal rear projection television. Referencenumeral 31 is a light source lamp. Reference numeral 32 indicates anoptical structural section. Reference numeral 33 indicates a liquidcrystal panel. Reference numeral 34 indicates a first mirror. Referencenumeral 35 indicates a projecting lens. Reference numeral 36 indicates asecond mirror. Reference numeral 37 indicates a screen. FIG. 13 is across section viewed in A-A section in the screen 37.

[0111] In FIG. 13, reference numeral 38 indicates a Fresnel lens.Reference numeral 39 is a micro-lens. Reference numeral 40 is a blackmatrix section. Reference numerals 43, 44, and 45 indicated light beamswhich are projected from image projection devices for three-primarycolors such as R, G, and B.

[0112] Embodiments of the present invention is explained as follows.

[0113]FIGS. 14A to 14C are views showing dual-lens sheets 30 a, 30 b,and 30 c according to embodiments of the present invention.

[0114] The lens sections 31 and 32 can be in any one of following forms(1) to (3) under condition that a front surface (projector and Fresnellens) is indicated as reference numeral 31 and a back surface (observer)is indicated as reference numeral 32.

[0115] A case (1) is a half-column-cylindrical-convex-lens in whichlongitudinal directions of the lens sections 31, 32 are the same (FIG.14A).

[0116] A case (2) is a micro-lens array section in which the unit lensis disposed in a secondary dimensional approximate matrix (FIG. 14B).

[0117] In a case (3), reference numeral 31 indicates thehalf-column-cylindrical-convex-lens unit, and reference numeral 32indicates the micro-lens array section in which the unit lens isdisposed in a secondary dimensional approximate matrix (FIG. 14C).

[0118] Here, as shown in FIGS. 5A and 5B, it is preferable that ashading layer 33 is formed on a non-light-condensing section by eachunit lens on a flat surface of at least one of the lens sheet (only alens sheet on an incident surface in the drawing) away from the lenssection so as to improve contrast in the display image when thedual-surface lens sheet is used in a display device having a rearprojection screen and a light source such as three-tube CRT projector.

[0119] By adapting a micro-lens array section in which the unit lens isdisposed under secondary dimensional approximate matrix condition for aunit lens to be used in either one of the front surface or the backsurface instead of a half-column-cylindrical-convex-lens, it is not anabsolute requirement to provide a light diffusing layer havingsufficient light diffusing characteristics in a certain position such asa rear projection screen having a conventional lenticular sheet.

[0120] The reason is as follows. In order to control the perspectiveangle (scope) of the display light by a conventional lenticular sheet,it is possible to control only in a horizontal direction by using thelens function; thus, the control in a vertical direction depends on alight diffusing layer. In contrast, by using the micro-lens arraysection according to the present invention, it is possible to controlthe perspective angle (scope) not only in a horizontal direction and avertical direction but also in every directions.

[0121] It is preferable that the disposition pitch of the unit lensesnear the lens section 31 is 0.3 mm or narrower, the disposition pitch ofthe unit lenses near the lens section 32 is 0.15 mm or narrower. Inorder to form a lens section in fine pitch, it is preferable to use aphoto-polymer method (hereinafter called 2P method) by which the lenssection made of a reacted hardened product ofradioactive-resin-curable-resin is bonded on a surface of a base board.

[0122] In a micro-lens array section, a unit lens is disposed on asurface of a base board under an approximate matrix condition. There isno limitation for the disposition method. A matrix disposition in whichthe unit lenses are neatly disposed under matrix condition, a deltadisposition, and a honeycomb disposition can be acceptable (FIGS. 2A to2D).

[0123] Also, it is not necessary that the shape of the unit lens is in asymmetrical and complete round when viewed in a plan view; thusasymmetrical shape is acceptable. Also, in case in which the shape ofthe unit lens is oval, it is not necessary to align major axis and minoraxis in all regions.

[0124] Furthermore, cases in which the neighboring unit lenses arecontacting or separating are also acceptable.

[0125] Also, in order to form a shading layer on a flat surface of thebase board which is disposed on the micro-lens sheet so as to be awayfrom the lens section, a method in which a photosensitive layer (a knownmember of which adhesion is lost by exposing a light) is formed onentire surface of the flat surface, and the photosensitive layer isexposed by the micro-lens array so as to change the characteristics ofthe photosensitive layer in an area corresponding to a light-condensingsection, and ink and a toner are attached to an area as anon-light-condensing section (know method called self-alignment by thelens it self) is preferable so as to form a shading layer in accuratepositions (not shown in the drawings).

[0126] In the drawings, it is defined that the neighboring unit lensarea indicates a case in which unit lenses contact by member (ofrectangle such as hexagon, etc.) Here, the shape of the unit lensdefined in the present invention is rectangle as shown in FIGS. 2A and2C. In case of FIG. 2B, the shape of the unit lens defined in thepresent invention is a triangle. In case of FIG. 2D, the shape of theunit lens defined in the present invention is hexagon. In case of FIG.2A, a lens section (curvature) which is indicated by a circle in theunit lens is provided. It is acceptable that overall unit lens havingshapes such as rectangle, triangle, hexagon constructs a lens section(curvature). Here, it is defined that neighboring unit lenses indicate acase in which the unit lenses are contacting by their member ofrectangles in a case of FIGS. 2A to 2D. Also, it is defined thatdisposition pitch between the unit lenses indicates a distance betweencenters of the unit lenses.

[0127] In cases of FIG. 2a (square), FIG. 2B (regular triangle), FIG. 2D(regular hexagon), disposition pitch between the neighboring unit lensesis uniform. In case of FIG. 2C (rectangle), it is understood that thedisposition pitch of the unit lenses in an array n and the dispositionpitch of the unit lenses in an array n and an array n+1 are different.

[0128] Here, in case of disposition shown in FIG. 2A, as explained in acase of FIG. 1, it is anticipated that the neighboring unit lenses 13are contacting. Also, it is anticipated that the neighboring unit lenses13 are separating.

[0129] In cases of dispositions shown in FIGS. 2B, 2C, and 2D, there isa finer periodicity (periodicity of 100 μm made by a combination ofperiod a and period b in an example shown in FIG. 2C) than that of thedisposition pitch (tentatively, 100 μm) between the unit lenses 13.Thus, moiré which is caused by pitch ratio in the projected pixel fromthe projector can be further reduced; therefore, the present inventionis superior.

[0130] Also, a position of a valley part from a top of the lens(distance from a surface of a base member) is determined by curvatureshape of the unit lens. In case in which the unit lens is in a symmetricsquare shape or symmetric hexagonal shape, such as position differsaround the unit lens.

[0131] The shape of curvature of the unit lens may be spherical oraspherical. Also, it is necessary to control the shape of the concavesection severely such that the diffusing characteristics in a horizontaldirection and a vertical direction should be controlled so as to bedifferent each other.

[0132] Also, in order to form a shading layer on a flat surface of thebase board 11 which is disposed on the micro-lens sheet 10 so as to beaway from the lens section, a method in which a photosensitive layer (aknown member of which adhesion is lost by exposing a light) is formed onentire surface of the flat surface, and the photosensitive layer isexposed by the micro-lens array so as to change the characteristics ofthe photosensitive layer in an area corresponding to a light-condensingsection, and ink and a toner are attached to an area as anon-light-condensing section (know method called self-alignment by thelens it self) is preferable so as to form a shading layer in accuratepositions (not shown in the drawings).

[0133] Second Embodiment

[0134] For a second embodiment according to the present invention, it ispreferable that a diameter of the unit lens shown in FIGS. 5A and 5B,and its disposition pitch is 200 μm or narrower so as to form a screenwhich is preferable for observing a fine resolution image.

[0135] Such a fine pitch operation can be obtained by performing amolding operation for forming a lens according to 2P method(photo-polymer method) by using the hardened product of theradioactive-ray-curable-resin.

[0136] In an example shown in FIG. 5, a lens section having asphericalshape with 80 μm diameter is formed on one surface of the transparentsupporting member 3 having 1.50 refractive index and 75 μm thicknessaccording to 2P method by using the hardened product of theradioactive-ray-curable-resin.

[0137] In a case of example shown in the above drawings, the maximumwidth of the chromatic difference of magnification is 6 μm (7.5% to thediameter of lens); thus, it is possible to form BM with 92.5% of shadingratio.

[0138] Even if the same material is used in the same dimension, in casein which the shape of the unit lens is spherical, the maximum width ofchromatic difference of magnification is 30 μm (37.5% to the diameter ofthe lens); thus, the maximum available shading ratio of BM is 62.5%.

[0139] By using by one piece of the above micro-lens sheet or aplurality of micro-lens sheet in a connected manner in a rear projectiondisplaying device having 30 inch size or larger, it is possible to watchhigh contrast image with wider perspective angle.

[0140] In case of a micro-lens sheet, comparing to a case of lenticularsheet having cylindrical lens group, the connected part of the lenssheets do not look seamy; thus, there is less disadvantage for alarge-size display.

[0141] Also, in the above case, a Fresnel lens sheet is disposed to aprojector as an image light source, it is possible to shorten thedistance between the projector and the screen when parallel lights areincident to the micro-lens sheet. By doing this, it is possible not onlyto reduce the size of the displaying device but also emit the displayingimage light having high brightness only to a necessary range; thus, itis preferable.

[0142] Also, in the above case, it is acceptable that a light diffusinglayer in which a light diffusing agent is dispersed is disposed in theFresnel lens and/or the micro-lens sheet.

[0143] For a light diffusing agent to be used here, a particle made frominorganic member such as silicon, aluminum, calcium, inorganic powderand glass beads containing oxide of these member, organic member such asacrylic resin, styrene resin, polycarbonate resin, acrylic/styrenecopolymer resin can be named.

[0144] In order to select the light diffusing agent, it is necessary totake following factors into account such as optical characteristics suchas refractive index difference to a binder resin, illumination on itssurface, dispersion for forming a light diffusing base member or lightdiffusing ink, and fragility during a molding operation. For an averagediameter of the particle, 5 μm or larger is preferable. More preferably,5 to 20 μm, further more preferably, 5 to 10 μm is preferable.

[0145] By compatibly use the light diffusing layer, it is possible tocontrol the perspective angle by alleviating the steepness of thebrightness reduction even in distant observing direction. Also, there isan improvement in focusing function by using gaps (mat surface) in afine lens array. In addition, there is an improvement in focusingfunction for image light.

[0146] The finer the unit lens is, the more similarly the surface of thelens section of the micro-lens sheet works. Therefore, there is lessdependency to the light diffusing layer using the light diffusing agent.In contrast, in a case in which there is not sufficient focusingcharacteristics and light diffusing characteristics only by the surfaceof the lens, the light diffusing layer is compatibly used.

[0147] Also, for a projection screen, the above micro-lens sheet can beused not only to a rear projection displaying device but also to a frontprojection displaying device having 30 inch size or larger if themicro-lens sheet.

[0148] When the above micro-lens sheet is used for a reflection screen,a light diffusing layer is formed on an entire surface of the micro-lenssheet away from the lens section.

[0149] Furthermore, it is possible that the above micro-lens sheet isused for a light guiding member for controlling the lighting light fromthe light source such that the lighting light is emitted so as be in auniform brightness in a uniform emitting direction in a display screen.

[0150] For such a representative displaying device, a liquid crystaldisplaying device (monitor or mobile terminals, etc.) having a backlightcan be named.

[0151] Third Embodiment

[0152] Embodiments of a projection screen as an example for the presentinvention is explained as follows with reference to the drawings.

[0153]FIGS. 8A and 8B are general views for an element lens of amicro-lens sheet used in a projection screen according to the presentinvention.

[0154]FIG. 9 is a perspective view of an element lens contained in themicro-lens array sheet used in the projection screen according to thepresent invention.

[0155]FIG. 10 is a cross section of an element lens in a verticaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0156]FIG. 11 is a cross section of an element lens in a horizontaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0157] Here, regarding the lens array sheet shown in this embodiment,the shape of the lens are actually designed, and these drawings are madeaccording to these designed lens shape.

[0158] In FIG. 8B, thickness (distance from a flat surface which is awayfrom the lens surface to a top of the lens) of an entire lens sheet isuniform. In case of a unit lens having symmetric toric shape, thedistance from the top of the lens to a valley part is different indistance D1 in A-A′ cross section and distance D2 in B-B′ even in thesame unit lens.

[0159] Main feature of the lens array sheet is in a shape of the elementlens contained in the lens array layer. The lens array layer comprises abase member layer in a board manner and a lens layer which is disposednear there.

[0160] The element lens contained in the lens array is in an asphericalshape. The element lens also is asymmetrical to an axis of the lenshaving geometrically three-dimensional shape. In its cross section,aspherical shapes such as not only aspherical shape, but also ovalshape, parabolic shape, and an aspherical shape including higher termsare included.

[0161] By using such a lens having aspherical and asymmetrical shape,the incident light (3) which is incident in parallel direction to theelement lens are refracted according to the incident position on aincident surface (1) due to difference of refraction angle at the timeof light emission. As a result, it is possible to differentiate therefractive index of the light to an orthogonal axis of coordinates on asurface which is orthogonal to the optical axis (equivalent to ahorizontal axis and a vertical axis in a screen which is disposedperpendicularly); therefore, it is possible to obtain a lightdistributing characteristics according to the purpose (see FIGS. 10 and11).

[0162] More specifically, as shown in FIGS. 10 and 11, there is aphenomena that the light condensing position of the emitted light (4) isdifferent in a thickness direction. The light emission angle of thelight at that time is equivalent to the light distributing anglecharacteristics.

[0163] For a lens array layer, plastic member which is as transparent asplastic member and glass member is preferable. Furthermore, a plasticmember which can be limitlessly used for an optical member is morepreferable from a production efficiency point of view.

[0164] For such a plastic member, acrylic resin such aspolymethyl_methacrylate, polycarbonate resin, acrylic-styrene copolymer,styrene resin, polyvinyl chloride resin can be named.

[0165] Also, for a member for a lens layer, aradioactive-ray-curable-resin such as an ultraviolet-ray-curable-resinor an electronic-ray-curable-resin should preferably be used because itis possible to perform a fine-pitch-forming operation. For such aradioactive-ray-curable-resin, for example, components containingurethane (meth) acrylate, and/or epoxy (meth) acrylate oligomer to whicha reacted diluted agent, photopolymerization starting agent, opticalsensitizer are doped can be used. An urethane (meth) oligomer, althoughthere is no particular limitation, can be obtained reacting, by forexample, polyols such as ethylene glycol, 1,4-butanediol, neopentylglycol, polycaprolactone polyol, polyester polyol, polycarbonate diol,polytetramethylene glycol, and polyisocyanates such as hexamethylenediisocyanate, isophorone diisocyanate, tolylene diisocyanate, xyleneisocyanate. Epoxy (meth) acrylate oligomer can be obtained by reactingepoxy resins such as bisphenol-A type epoxy resin, bisphenol-F typeepoxy resin, phenol novolak type epoxy resin, terminal glycidyl ether ofbisphenol-A type propylene oxide adduct, and fluorine epoxy resin and(meth) acrylic acid.

[0166] A lens array layer can be produced, for example, as follows. Aradioactive-ray-curable-resin is applied on a base member layer made ofa plastic member under condition that the radioactive-ray-curable-resinis not hardened. From above there, a molding stamper is pushed, and apredetermined radioactive ray is emitted so as to harden it. Thus, alens layer is formed.

[0167] A molding stamper can form a lens layer, for example, in afollowing manner. By using a photo-lithography method, at first, aplurality of mask on which a cross sectional shape for the element lensis patterned are prepared. By using the masks, silicon wafers areexposed consequently. After that, by performing an etching operationsuch as RIE. Patterning operations are repeated in its depth direction;thus, a molding stamper having a designed shape can be obtained.

[0168] As explained above, a lens array sheet layer can be produced bythe same method as used for producing a conventional lenticular lens.

[0169] A photosensitive resin layer and a shading layer can be producedas follows. Fresnel lenses are disposed in parallel under the samecondition as the practical use for a projection screen. A light isemitted from the lens layer of the lens array sheet via the Fresnellenses. The characteristics in the photosensitive resin layer in a partwhich is exposed by the light which passes through the lens array layerchanges, and adhesive characteristics is lost. The, a transfer filmhaving a black transfer layer containing a black carbon is pushed to thephotosensitive resin layer. Accordingly, the transfer layer istransferred to an unexposed region having adhesive characteristicsselectively. Thus, the shading layer is formed.

[0170] The shading layer is formed corresponding to the focusing patternin a line-segment state due to the light condensation because of thetoric micro-lens. The position of such focusing pattern represents anastigmatism due to the toric micro-lens approximately. Therefore, thefocusing pattern appears in two points in an optical axis direction(thickness direction). Among these focus points (called, in a field ofgeometric optics, a sagital focus point and a meridional focus point),the most preferable position for forming the lens sheet is adjusted byperforming a sandwiching adjustment for low refractive index layer(otherwise, the lens is designed a such). By disposing a black shadinglayer in this position, it is possible to obtain a high rate BM pattern.Here, a lower refractive index layer is used. This is because of itsweak refractive force; thus it is possible to anticipate largertolerance for thickness; therefore, it is possible to improve itsformability.

[0171] Consequently, on this shading layer, by disposing an adhesiveagent layer, light diffusing layer, and a hardcoat layer according tonecessity, it is possible to obtain a lens array sheet.

[0172] As explained above, in this lens array sheet, by preferablydesigning a shape of one toric lens array, it is possible to control thelight distributing characteristics (perspective angle) of a light whichtransmits through the lens array sheet in both a horizontal directionand a vertical direction. In particular, by making its ratio at ⅔ orlower, it is possible to distribute the vertical/horizontal lightdistributing characteristics for a preferable projection screen. Thus,it is possible to obtain preferable characteristics for a screen.

[0173] Furthermore, it is possible to reduce cost for members used inthe production and manufacturing process compared to a case in which twolens layers are used or the lens layers are formed on both surfaces ofthe base member layer.

[0174] Also, by simplifying the light diffusing layer, it is possible toreduce the absorption of the light or decrease of gain in the lightdiffusing layer. As a result, it is possible to control white-scatteringphenomena which is caused by the light diffusing layer; thus, it ispossible to realize high S/N ratio.

[0175] Furthermore, by adding the Fresnel lens, it is possible toshorten the emission distance from the projector. By establishing suchcompatibility, it is possible to obtain a superior screen.

[0176] Here, there is no particular limitation in factors such asthickness of each layer of the lens array sheet according to the presentinvention, and pitch of the lens array. These factors can be changedpreferably.

[0177] Experimental Example

[0178] The present invention is explained with reference to experimentalexample more specifically as follows.

[0179] In this experimental example, designing parameter is determinedas follows. Effect in the present invention is examined.

[0180] Designing Parameter

[0181] In a base member layer of the lens array layer is made frompolyethylene terephthalate with 0.075 mm thickness. Lens layer in thelens array layer is made such that the material is UV photosensitiveresin, pitch between the lenses is 0.080 mm, the shape of cross sectionin which the lens thug (height of convex section of the lens) is large(corresponding to a horizontal direction in the screen) is oval, thecross section in which the lens thug is small is spherical, ratio ofthug amount is 2:1 so as to form a toric shape. For a photosensitiveresin layer, a Cromalin film (Trademark, registered by DUPONT) having 20μm thickness is used.

[0182] To a surface of the lens on this lens array sheet, parallel lightwhich is collimated in 1 to 5 degrees is emitted so as to perform apatterning operation for the photosensitive layer. Then, a black filmhaving 2 μm thickness (transfer film of carbon black) is transferred soas to be a shading layer; thus, it is possible to obtain a shading layerhaving an aperture corresponding to a micro-lens contained in the lensarray.

[0183] The lens array surface of the lens array sheet which is obtainedin this way is disposed toward the light source. By using the lens arraysheet for diffusing the light, it is possible to observe that theperspective angle corresponding to a shape of the lens array can beobtained respectively.

INDUSTRIAL APPLICABILITY

[0184] By using a dual-surface lens sheet according to the presentinvention is used for a rear projection screen which is used in adisplay device which uses a plurality of projector as light sources suchas a three-tube CRT projector, there are effects in that the color shiftis reduced, there is no problem of alignment of the unit lenses on afront surface and a back surface even if the unit lenses are disposed infine pitch, and manufacturing process can be simplified.

[0185] According to the micro-lens sheet in the present invention, it ispossible to control the light emission direction (range) of the displaylight from the lens section so as to be wide in a perspective range bydisposing the unit lens group in fine pitch such as 200 μm or shorter.

[0186] In particular, according to the present invention, it is easy toform a black matrix with fine pitch such that the borderline between theaperture section and the shading section is clear so as to form a blackmatrix having high shading rate (75% or higher) on the micro-lens sheetaway from the lens section.

[0187] Furthermore, according to the micro-lens sheet having amicro-lens array section which is used for the projection screenaccording to the present invention, it is possible to control the lightdistributing characteristics of the transmitting light through the lensarray layer in a vertical direction and a horizontal direction bypreferably changing the shape of toric shape of the element lens. Thisfact indicates that it is possible to control the opticalcharacteristics of the screen positively; thus, there is a great effectin reducing the time and cost necessary for product development.

[0188] Also, it is possible to set the perspective angle independentlyin a vertical direction and a horizontal direction on one piece ofmicro-lens sheet desirably. Therefore, (1) it is possible to reduce thecost necessary for production and (2) it is not necessary to develop andprepare the necessary material because the amount of the light diffusingagent can be set according to the available material. Also, (3) it ispossible to restrict the absorption of the light (light loss).Therefore, there is an effect in that it is possible to obtain a brightprojection screen using the micro-lens sheet easily.

[0189] Also, it is possible to reduce the amount of the light diffusingagent comparing a case of the conventional screen. Therefore, reflectionand scattering of the external light are restricted; thus, transparencyincreases. Therefore, light absorbing function in enhanced. Thus, it ispossible to obtain a projection screen using the micro-lens sheet havingconventionally unrealized improved S/N.

1. A dual-surface lens sheet having periodical gaps contained in a lenssections on a front surface and a back surface in a lens sheet whereinpitch ratio of the unit lens on the front surface and the back surfaceis in a range of 1:1 to 1:30.
 2. A dual-surface lens sheet according toclaim 1 wherein the lens sections on the front surface and the backsurface are half-column-cylindrical-convex-lenses which are disposed inuniform disposition direction.
 3. A dual lens sheet according to claim 1wherein the lens sections on the front surface and the back surface aremicro-lens array section in which the unit lenses are disposed undercondition of secondary dimensional approximate matrix.
 4. A dual lenssheet according to claim 1 wherein one of the lens sections on the frontsurface and the back surface is a half-column-cylindrical-convex-lensgroup and the other one is a micro-lens array section in which the unitlenses are disposed under condition of secondary dimensional approximatematrix, pitch in which the unit lens in thehalf-column-cylindrical-convex-lens group is disposed is 0.3 mm or less,pitch in which the unit lens in the micro-lens array section is disposedis 0.15 mm or less.
 5. A dual lens sheet according to claims 3 or 4wherein the micro-lens array section is made of a reacted product of aradioactive-ray-curable-resin and includes the unit lens havingaspherical shape.
 6. A dual lens sheet according to claims 3 or 4wherein the micro-lens array section includes only a unit lens havingaspherical shape.
 7. A dual lens sheet according to claims 3 or 4wherein, in the micro-lens array section, optical diffusion by the lensfunction in each unit lens is different in a horizontal direction and avertical direction.
 8. A dual lens sheet according to claim 1 whereinperiodical gaps are formed for forming the lens section on one surfaceof the micro-lens sheet, the other surface is flat, the lens sheets arelayered such that the flat surfaces of each sheet are corresponding. 9.A micro-lens sheet according to claim 8 wherein a shading layer isformed in an area corresponding to a non-light-condensing section byeach unit lens on a flat surface of at least one of the lens sheet awayfrom the lens section.
 10. A dual lens sheet according to claim 1wherein a unit lens having convex shape is disposed in the lens section,a focusing surface of at least one of the lens section exists in thedual lens sheet, parallel lights which is incident to one of the unitlens pass through a plurality of unit lens in the other lens sectionwhen emitted from the lens section in the other lens section.
 11. A rearprojection screen in which a dual-surface lens sheet according to claim1 and a Fresnel lens are assembled wherein a lens section in which theunit lens in the dual lens sheet is disposed in larger pitch and thelens section in the Fresnel lens sheet are faced such that the Fresnellens sheet is disposed near a plurality of projector (light source). 12.A display device having a three-tube CRT projector as a light source anda rear projection screen according to claim
 11. 13. A micro-lens sheethaving a micro-lens array section in which unit lenses are disposed inapproximate matrix in a second dimensional manner on at least onesurface of a base board wherein diameter for each of the unit lens andthe disposition pitch is 200 μm or shorter; light emission angle whichis emitted from each unit lens is more than ±30 degrees against a normalof a main surface of the micro-lens sheet; chromatic difference ofmagnification which is caused by each unit lens is designed to be in arange of 0% <chromatic difference of magnification ≦50% of the diameterof the lens.
 14. A micro-lens sheet according to claim 13 wherein ashading layer is formed on another surface of the base board which isdisposed away from the micro-lens array section such that alight-condensing section by each unit lens become an aperture section.15. A micro-lens sheet according to claim 14 wherein the shading layerif formed so as to have an area which is 75% of an entire area of themicro-lens array section or larger.
 16. A micro-lens sheet according toclaim 14 wherein the shading layer is formed on a surface of thenon-light-condensing section on a photo-sensitive resin layer in whichthe light-condensing section and the non-light-condensing section areformed according to the light-condensation of the micro-lens arraysection.
 17. A micro-lens sheet according to claim 16 wherein thephoto-sensitive resin layer is formed on a surface of the base boardwhich is away from the micro-lens array section via a transparent resinlayer having lower refractive index than that of the base board or thephoto-sensitive resin layer is directly formed on a surface of the baseboard so as to have lower refractive index than that of the base boardsuch that the photo-sensitive resin layer is disposed away from themicro-lens array section.
 18. A rear-projection screen which size is 30inches or larger using the micro-lens sheet according to claim
 13. 19. Aprojection screen according to claim 13 wherein the Fresnel-lens sheetis disposed on the projector as a projection light source.
 20. Aprojection screen according to claim 18 wherein the light-diffusionlayer in which a light diffusion member is dispersed is disposed neareither one of the Fresnel-lens sheet or the micro-lens sheet.
 21. Afront-projection screen which size is 30 inches or larger having themicro-lens sheet according to claim 13 and the light-reflection layerwhich is disposed on a surface of the base board which is opposite tothe lens.
 22. A display device having a backlight having the micro-lenssheet according to claim 13 as a light-guiding member for controlling alight emission from the light source under condition of uniformbrightness or in a uniform emission direction in a display screen.
 23. Aprojection screen having the micro-lens sheet having the micro-lensarray section in which the unit lenses are disposed in an approximatematrix in a second-dimensional manner wherein a surface of the unit lensis formed in toric shape as a continuous surface such that curvature ofcross sectional shape of the unit lens in one direction is smaller thanthat in an orthogonal direction to the particular direction; themicro-lens array section in which the unit lens is disposed in anapproximate matrix in a second-dimension manner is formed on one surfaceof the transparent sheet; and the shading layer having the aperturesection of which optical axis is aligned with the optical axis of unitlens group on a surface of the sheet which is disposed opposite to themicro-lens array section.
 24. A projection screen according to claim 23wherein directions of the curvature of each unit lens are uniformlydisposed when the micro-lens array section in which the unit lens isdisposed in an approximate matrix in a second-dimension manner is formedon one surface of the transparent sheet.
 25. A projection screenaccording to claim 23 wherein lens thug of the toric surface which is aratio between thickness of a curvature section in a one direction andthickness of a curvature section in a cross sectional surface in anorthogonal direction is ⅔ or smaller.
 26. A projection screen accordingto claim 23 wherein lens thug of the toric surface which is a ratiobetween thickness of a curvature section in a horizontal direction andthickness of a curvature section in a cross sectional surface in avertical direction is ⅔ or smaller.
 27. A projection screen according toclaim 23 wherein the micro-lens array section is formed on one surfaceof the transparent sheet which is disposed in an area from which a lightis incident (near a projector) when the micro-lens array section is usedfor a transparent projection screen.
 28. A projection screen accordingto claim 23 wherein the shading layer is formed in thenon-light-condensing area on a surface of a base board opposite to thelens such that a light does not condense by exposing a light through themicro-lens array section; the photosensitive resin layer or a layerwhich is formed on a surface of the photosensitive resin layer is a baseboard for a lens such that the refractive index of the layer is lowerthan that of the transparent sheet.
 29. A projection screen furtherhaving a Fresnel lens having a concentric ring band near a lightincident region (near a projector) when the projection screen accordingto claim 23 is used for a transparent projection screen.
 30. Aprojection screen according to claim 29 wherein a shape of a unit lensarea is triangular, hexagonal, or rectangular.